1. Field of the Invention
The present invention relates to a projection display, and more particularly, to an illumination system of optical engine for projection display, and specifically, to a cooling apparatus of illumination optical engine for projection display.
2. Description of the Prior Art
With the rapid development of optical electronic technologies, conventional projection display apparatus usually uses a high power light bulb as the light source for illumination system in order to have a brighter and clearer image on the screen and provide a comfortable view environment to users. However, the high power light bulb creates the problem of high heat dispersion temperature in the mean while. In order to cool the heat generated by the high power light bulb and the optical components of the illumination system, and further avoid the optical components from deteriorating due to the high temperature. The illumination system of optical engine in the prior art projection display uses fans for the cooling. However, due to the fact that the light bulbs and optical components that require cooling are widely spread out, multiple cooling fans have to be installed, and causing a noise problem with noise. Therefore, the way of effectively dispersing heat and reducing noise becomes an important research and development subject for the projection display industry.
As illustrated in FIG. 1, the optical engine of the projection display apparatus of the prior art mainly consist of an illumination system 10 and an imaging system 20, wherein the illumination system 10 has a light bulb as the light source 11 installed inside the lamp base 111 for projecting a light beam, wherein the light beam projects into the first lens array 12 inside the lens framework 17. The first lens array 12 is composed of numerous micro-lenses, which produces uniform light beam, wherein the first lens array 12 facts the light source with its back surface, the back surface of the lens array 12 is coated with a layer of ultraviolet-infrared cutter (UV-IR cutter) 121 for filtering the invisible light beam. Therefore the amount of such useless and invisible ultraviolet, infrared light beams projecting into the optical projection system can be reduced, so as to prevent the temperature of the optical components from increasing. After passing through the first lens array 12, the light beam is diverted via the reflection mirror 13 positioned slantwise in front of the first lens array 12, then projected into a second lens array 14, wherein the second lens array 14 fronts the light source with its back surface, the back surface of the second lens array 14 is coated with a layer of ultraviolet-infrared cutter (UV-IR cutter) 141. The light beam is then passed through a polarizing convert system (PCS) 151 which contains a layer of polarizing film 151, and a condenser lens 16 for converging light beam, and projecting to an imaging system 20.
The imaging system 20 separates the light beam into red and other visible beams via a first dichroic mirror 21. Thered light beam is reflected by the first dichroic mirror 21 and passed onto the first reflection mirror 211, then passed through the first lens set 212 that is composed of retarder plate, liquid crystal displayey (LCD), and polarizer, and finally projected onto the X-prism 24. The other visible beams are directly passed through the first dichroic mirror 21, and projected onto the second dichroic mirror 22 for separating into light beams of blue and green colors. The blue light beam is reflected via the second dichroic mirror 22, projecting through the second lens set 221 that is composed of polarizer retarder plate, liquid crystal display (LCD), and polarizer, and finally projected onto the X-prism 24. The green light beam is directly projected through the second dichroic mirror 22, and passed through the third reflection mirror 222, the fourth reflection mirror 223 and the third lens set 224 that is composed of the retarder plate, the liquid crystal display (LCD), and the polarizer. Then project the green light onto the X-prism 24. The X-prism combines the red, blue and green light beams and projects on the screen (not shown in drawing) via a projection lens 25.
In the optical engine application of the prior art, where high power light bulbs are used as the light source for projection, apart from the high heat of the light bulb as the light source that needs to cool, the first lens array 12 that gets the projection first also experiences an increase in temperature, as it takes most heat energy. When the projection temperature raise to the limitation, due to the ultraviolet-infrared cutter (UV-IR cutter) 121 and the lens array 12 are made from different materials, and thus having different coefficients of expansion, the layer of ultraviolet-infrared cutter (UV-IR cutter) 121 and the lens array 12 will be stripped off forming an interstice and affects optical quality. In addition, the light beam received by the second lens array 14, despite having been filtered through the UV-IR cutter 121 on the first lens array 12, still carries a fairly large amount of heat energy from the visible light beams. The layer of UV-IR cutter 141 on the second lens array 14 will also be stripped off when the temperature raises to the limitation. This stripping problem also affects the polarizing film 151 of the polarization system 15. Furthermore, high temperature also affects the optical quality of all the optical components in the imaging system 20. However, since the characteristics of the present invention are limited to the illumination system 10, the cooling of the imaging system 20 is not described within the present invention, wherein the imaging system is not limited to the penetrated type of light valve system, and can also include the reflective type of light valve system.
In the projection display of the prior art, in order to lower the temperature of the illumination system, which installing cooling fans, respectively, at the locations of the light source 11, the first lens array 12, the second lens array 14, and the polarization systems 15. There are also some apparatus of the prior art using a larger cooling fan for cooling the light source 11 and the first lens array 12, at the same time, while using another smaller fan for cooling the second lens array 14 that is located farther away from the light source 11. Nevertheless, both of these two methods require the use of multiple sets of fans, not only increasing cost and noise, but also increasing the difficulty in system control, to such an extent that the it lowers the reliability of the system, while affecting the quality of the products.
The object of the present invention is to provide a cooling apparatus for illumination system of optical engine, wherein only one single fan is applied in order to reduce noise and lower cost, while improving the reliability of the system operation.
The other object of the present invention is to provide a cooling apparatus for illumination system of optical engine according to the required cooling air of each component to arrange differentiated interstice of the air duct to effectively utilize the air flow from fan and improving the cooling efficiency of the fan.
To achieve the above-mentioned objectives, cooling apparatus for illumination system on optical engine of the present invention includes: an illumination system that has a lamp base for its light source, wherein the lamp base has an air duct body fixed on one side of it, wherein at least one partition separates the air duct body into a plurality of air ducts of different surface areas, and an outer air duct extends one of the air ducts from underneath the air duct body to outside of the air duct body, wherein a fan installed on the air duct body takes in air through each of the air ducts and the outer air duct to cool the illumination system, thus improving the cooling efficiency of the fans, while reducing the volume of cooling air needed from the fans, lowering the cost and reducing the noise from the fans.